Relationship between antimicrobial activity, phenolic profile and antioxidant capacity of murta (Ugni molinae Turcz) extracts prepared by different drying methods

BACKGROUND: Murta, a native berry from southern Chile, has been used in Chilean folk medicine to treat inflammatory and infectious diseases among other ailments. OBJECTIVE: This work assessed the influence of different drying methods: freeze drying (FD), convective drying (CD), vacuum drying (VD), sun drying (SD), and infrared drying (IRD) on the antimicrobial activity of murta berries against four microbial species. METHODS: Murta berries were subjected to five drying methods. Measurement of bioactive compounds that include: phenolic compounds by HPLC, total flavonoid content by a spectrophotometric method; and anthocyanins by HPLC-MS. Determination of antioxidant capacity by DPPH and ORAC methods and antimicrobial activity by means of agar well diffusion assay. RESULTS: Murta extracts obtained by FD and CD showed the highest antimicrobial activity, with Staphylococcus aureus the most susceptible species. Drying induced a significant loss of bioactive compounds and antioxidant activity although minimal losses were observed in FD, CD and VD extracts. In these extracts, the abundance of bioactive compounds correlated with the antimicrobial activity. Eight phenolic compounds were identified in murta extracts where pyrogallol's abundance increased in all dried samples. CONCLUSIONS: Our results suggest that murta dried with FD, CD and VD have the highest potential to be used as a functional ingredient in the food industry.